Control means for superregenerative receivers



April 1930. R. A. CLAUSNITZER ,7 4,264

CONTROL MEANS FOR SUPERREGENERATIVE RECEIVERS Filed April 15. 1927 In venfar Fun; ALBA/Y (mus/v m A br'r/eg Patented Apr. 15, 1930 T F g RUDOLF ALIBAN CLAUSNITZER, F LUBECK, GERMANY CONTROL MEANS FOR SUPERREGENERATIVE RECEIVERS Application filed April 15, 1927, Serial No. 184,088, and in Germany January 18, 1927.

The hitherto known single super-regenerative-receiver, used for high frequency telegraphy and telephony gives extraordinarily great ranges by the combination of a high frequency-valve-circuit of tightly negative effective resistance to a source of alternatingcurrent of auxiliary-frequency. The auxiliary-frequency is superimposed on the high-frequency valve-circuit'of negative cffective-resistance.

The method of working is as follows :The auxiliary frequency constantly changes the effective resulting resistance,that is to say the damping of the super-regenerative circuit,changes it from negative to positive values (of damping), and conversely. Let it be assumed, that during the first halfoscillation of the auxiliary-frequency, the damping (the eflective resistance) of the 2 grid-circuit is for instance strongly negative; small impulsesfor instance the high frequency oscillations of a distant transmitter, impressed by means of the (loop-) antenna on the super-back-coupled grid circuitwill be built or set up as free oscillations to a maximum which depends on the strength of the impulse and on the duration of the negative damping. It is therefore already possible, by means of the hitherto known super-regenerativecircuits to work with a receiver having a temporarily negative damping. Before however the saturation of the valve in these super-regenerativecircuits is reached, or even exceeded under the action of the natural-oscillation which is being built up, the second half-oscillation of the above mentioned auxiliary-frequency will bring the damping ofthe high frequency grid-circuit to positive values. Owing to the now existing positive damping, the released free oscillation will at once die out. This process will be constantly repeated (about 20,000 times per second). The auxiliary-frequency will reproduce therefore once in each 4 period the hypersuper-sensitive state of the negative-dmmping in the super-regenerativereceiving-circuit.

The working of this single super-backcoupling tends therefore to operate in jerks.

A singlesuper-regenerative-circuit also gives a drive during the first half-period (halfcycle) of the auxiliary frequency; during the other half-period the high-frequency-circuit goes to rest.

The high-frequency amplification which can be obtained by means of this periodically negative damping, is the multiple of a simple back coupling. (When larger receivingvalves or the smallest transmitter-valves are used, it is possible, with wave-lengths round 300 meters to 400 meters, to take a superback-coupling as approximately equal to a two-stage back-coupling, that is to say to a two valve set known as a neutrodyne set.)

Since the invention of the super-regenerative-circuit or super-back-coupling (in 1922) it has been the aim of wireless engineers to use also a plurality of super-back-couplings in series in high-frequency stages that is to say, in a high frequency cascade, for long waves as well as for short waves.

The first attempt to use a multi-sta 'e-superback-coupling was described in: ome recent developments of regenerative-circuits, by Edwin H. Armstrong, (published in The Wireless World and Radio Review, 18th November, 1922, page 238, last paragraph, and page 239, London, and in The Institute of Radio Engineers, New York, June 7, 1922).

A super-baclccoupling as the first high-frequency-stage was tuned to the transmitteroscillations. In order to avoid different tones of the natural own oscillations of the two super-back-coupled high-frequency-systems which own oscillations are never equal to each other, the second super-back-coupling as the second high-frequency-stage, was tuned to the double frequency which exists almost as strongly in the anode-circuit of the first valve'. The direction (or distribution) of the working half-cycles and idle halfcycles in the time or tempo of the auxiliary frequency was effected in such a manner that two super-back-couplings were synchronously in the working-half-cycle, or simultaneously in the idle-half-cycle.

The present invention relates to a nonsynchronous distribution of the working and idle half-cycles of the neighboring superinductive-galvanic back-couplings, which half-cycles are set up by the auxiliary oscillation.

A constructional example of the invention is given diagrammatically in the accompanying drawings. Figure 1 represents a high and auxiliary frequency circuit arrangement with four amplifying stages for example; Figure 2 is an additional detector tube for the better rectification of the preliminary amplified high-frequency oscillations.

In the scheme of connections shown. in the drawings four amplifying stages are used, each of which is a super-regenerative-circuit A A A and A, in the individual stages the tubes are correspondingly marked a a a and a. The connections to the tubes a a 11 3a are coupling means which are known per se, in which 6 6 b and 6 represent grid circuits with additional damping means 0 0 c and 0 The first grid circuit 6 is attached to the frame antenna 1". Back coupling is effected by a plate coil d inductively coupled to the grid circuit, and is regulated by a condenser 6 The electric transmission of energy from stage A to A is effected by means of a coil f, The choking-coil g ensures the high frequency path through d 7, e V

The same arrangement as shown in the stage A is also shown by the following stages A and A the individual elementsin these stages are correspondingly designated a b 0 (1?, 6 f 9 etc. Inthe last stage A it is shown that in'steadof the inductive back coupling, use can also be made of another, for example one which forms a combination of or capacitive-galvanic back coupling d. The additional damping coil 0 is of great inductivity and of high ohmic resistance; it possesses the connecting terminals 1 and 2 for connecting the detector device D (Figure 2). The high-frequency energy collected by means of the coil 0 of the stage A is rectified in the detector tube h, and, as may be required or desired, can be heard through the telephone T. For carrying out the subject matter of the invention according to the constructional example, (Figure 1) the tubes a and a on the one hand and the tubes a and a on the other hand are mounted in connection with one common auxiliary or medium frequency oscillating circuit M. consisting of a condenser 70 and of a subdivided coil. 2' and 2' as a push and pull generator, so that all the tubes a a a and atoscillate not only in the frequency of this oscillating circuit M, but also in the highfrequency cycle, and. all four valves a a a a function in the production of two oscillations of difi'erent frequencies.

Corresponding to the push-pull connection in the grid circuits, the anode circuits of the tubes a a and a a respectively are combined together, the anode wires combined according to this principle are correspondingly designated with 12 p and 19 19, and the combined grid wires with +g and g +g The auxiliary or medium requency oscillating condition is maintained by means of the return coupling coils m m The supply of the anode energy takes place through point n. The suitable preliminary grid voltage for determining the working point of all four tubes a a a a in the bend of the tube characteristic =f(E is determined by the connection 0. Q

As in the regenerative system hitherto known the mean or auxiliary frequency also lies with this new connection at theboundary of the auditory limit of about 20,000 oscillations per second. p

According to the invention for instance the first super-back-coupling as the first highfrequency-stage and the third super-backcoupling as the third stage are in the state tion (direction) ofothe working periods or cycles is attained in the simplest manner by combining together the first and the third valve, and then the second and fourth valve, in the auxiliary-frequency-anodepath. These two groups of valves form together (on a common auxiliary-frequency-grid-circuit) a push-pull generator. As regards the highfrequency, each of the four valves is moreover super-back-coupled. The accompanying diagram of connections (Figure 1) shows fours valves asa four-stage super-back-coupling, but also two, three or perhaps even more super-back-couplings may work in series in accordance with the same principle. In place of the strong positive additional-dan'iping of the grid-circuits, a separate aperiodic detector-valve (Figure 2) may be coupled to the last super-back-coupling for the purpose of bettering the rectification of the high whereby in each super-back-coupling-stage the amplification increases essentially (see the coils of the grid circuits to b, Figure 1).

The basic advantage of this series-connection of super-back-couplings, is as follows If for instance the first (and at the same time the third) stage is at the beginning of its Working half-cycle, even an exceedingly Weak 1o transmitter-oscillation will become built up during this working half-cycle to a certain maximum in the natural-oscillation of the first, and only in this first super-back-coupled stage or system. This maximum is situated therefore, in point of time, at the end of the Working half-cycle. At this moment however the working half-cycle of the coupled next super-back-coupling, that is to say, of the second high-frequency-stage, sets in already. The second superback-coupling receives therefore at the beginning of its exceedingly sensitive period of negative damping, not onlyas hitherto-the high-frequency input oscillations which are made approximately stronger only by the amplification factor of the first high-frequency valve, but also the maximum of the natural oscillation of the preliminary stage already built up during the preceding half period. The maximum of the second stage is therefore already incomparably much higher than that of the first one. To the third super-backcoupling is now again supplied at the suitable moment-the beginning of its half period with negative damping-the maximum of the super-back-coupled second preliminary stage. In this third stage this radio frequency is built up to a third maximum, and so on.

As regards the telephony, (that is the low-. frequency modulation superposed on the high frequency) the process could be explained as follows The amplitude of oscillation of the carrier frequency at any moment, which gives the modulation, determines the value of the max imum of the natural oscillation of the first super-back-coupling, and of all the maximum values following in the next stages. Each train of high-frequency waves, which excites the input circuit to a greater or less degree in accordance with the value of the modulation at the moment, when the number of superback-couplings connected together in series is for instance a it will have time, durin it half periods of the auxiliary-frequency, f to the final rectification of the high-frequency) to become built up. It passes, with constant frequency-multiplication consecutively through all the super-back-couplings.

The basic connection of each single superback-coupling to the high-frequencypaths can be in principle any desired high-frequency generator-connection The use (operative or working) of the new 65 receiver-connection described in the foregoing, namely, the series-connection of superback-couplings, each characterized by two consecutive super-back-coupled high frequency valve circuits which work alternately can be either, with the assistance of tuning all single stages, that of a non-heterodyne receiver, or in the case of fixed stages having natural frequencies by receivers using a pre ceding frequency conversion, that of an intermediate frequency amplifier in a superheterodyne receiver.

At the first experiment carried out at Lubeck, Germany, with such a receiver having a two stage super-back-coupling only, the stages working alternately, it was found possible to get on the loud-speaker with a loopantenna of about one square-meter very strong telephony from the London 2 L. 0. station. A separation of all single frequency stages appears to be advantageous. Moreover attention must be paid to the suppression of acoustic back-couplings between the loudspeaker and the hyper-sensitive super-backcouplings.

Of the three kinds of periodic alteration of the damping of the super-back-couplings, which can be used in principle, the periodic alteration of the negative damping seems to be preferable in carrying out the invention from the practical point of view, and in view of the presence of higher harmonics.

I claim:

A radio receiving system comprising a plurality of amplifying stages connected in cascade, circuit means for super-regeneratively coupling each of said amplifier stages, an oscillator adapted to generate a lower auxiliary frequency and coupled to said amplifier stages, and means for tuning said amplifier stages to a higher harmonic of the frequency of each preceding stage, said super-regenerative circuits being so coupled in this auxiliary generator system that one of two neighboring amplifying stages is always in the phase of negative damping, while the other is in the phase of positive damping, whereby the high frequency oscillation in each amplifier stage will not excite the following stage before this osplillation has reached its maximum amplitu e.

RUDOLF ALBAN CLAUSNITZER. 

